In the past, as such a retractable writing implement, there is known a writing implement of which a shaft tube includes a knock body (operation part) configured to be capable of reciprocating in an axial direction; an intermediate member formed in the inner-surface side of the shaft tube so as to be opposed to the knock body; a rotor configured to engage with a cam slope surface of the knock body or a cam slope surface of the intermediate member so as to rotate in a circumferential direction; an urging member configured to urge the rotor backward; and an ink tank (refill) configured to be interlocked with the rotor. When the knock body is pressed, a protrusion of the rotor advances in an axial direction along a slide groove of the intermediate member. Subsequently, the protrusion comes off from the slide groove and rotates so as to slide along the cam slope surface of the knock body. Subsequently, when the knock body returns, the protrusion of the rotor engages with the lock concave portion of the intermediate member so as to be in a locked state. Subsequently, when the knock body is pressed again, the protrusion of the rotor comes off from the lock concave portion of the intermediate member so as to release the locked state, and rotates so as to slide along the cam slope surface of the knock body. Subsequently, the protrusion of the rotor in inserted into the slide groove of the intermediate member, and retreats in an axial direction (for example, see Patent Document 1).
However, according to the known retractable writing implement, since the ink tank is forcedly retreated by the urging member in terms of a releasing operation, a backward shock (hereinafter, referred to as ‘back shock’) is generated when the ink tank returns to a normal position. Accordingly, air is introduced from a writing tip portion so that ink easily flows to the ink tank in a reverse direction. As a result, faint writing or writing failure may occur during a writing operation.
Particularly, in a case where oil-based ink having low viscosity and low flow resistance is received in the ink tank, a problem arises in that the faint writing or the writing failure easily occurs during the writing operation due to the back shock.
In addition, since shock sound is generated when the retreating ink tank returns to the normal position, and generally the urging force is strongly set in order to surely allow the writing tip portion to appear or disappear, a problem arises in that large shock sound is easily generated when the writing tip portion disappears.
Since a slight gap is formed therebetween in order to reciprocate the knock body in the shaft tube, a part thereof in a circumferential direction come into sliding contact with each other in a surface shape when the knock body reciprocates in terms of the knock operation, and thus slide movement sound is generated. When the rotor rotates with respect to the knock body, bouncing sound or shock sound is generated among the knock body, the rotor, and the intermediate member.
The sounds are generally called knock sound, but since the general knock sound is similar to sharp and high sound ‘tick’, ‘tick’, and a knock feeling is light in order to obtain good operability, meaningless knock operations may be continuously repeated to continuously generate the knock sound. Because of a frivolous image together with such a behavior, some persons do not like the retractable writing implement itself.
Since a user himself/herself may use such so-called knock sound to check an operation state (where the writing tip portion appears or disappears), it does not give an unpleasant feeling of course, but may give an unpleasant feeling to other persons. Particularly, during a meeting when the surrounding is silent, a problem arises in that the knock sound in terms of the meaningless knock operations gives an unpleasant feeling to other persons.    Patent Document 1: JP-A-2004-209881 (Pages 6 and 7, FIGS. 1 and 2)